February 22, 2016 - ISRAEL - Flash floods hit eastern Israel as temperatures drop throughout country; warmer days expected later in the week

Several Israeli schools and roads were closed Monday due to flooding as
rain and wind bashed the country after a week of unseasonably high
temperatures.

Flash floods in the area of Ein Gedi in eastern Israel prompted school
closures in the area. On Mount Hermon, heavy snow and wind led operators
to close the ski resort.

A group of 10 hikers who were stranded due to the inclement weather in
the Negev, next to the Ramon Crater in southern Israel, were rescued. A
search and rescue unit was called to the area and safely brought the
hikers out using jeeps, reports said.

The southern city of Sderot also experienced flooding, as well as many Bedouin areas of the Negev.

WATCH: Heavy rainfall and widespread flooding in Israel.

"I don't understand why this happened to us. The last time, the
municipality told us that [there was flooding] because there was more
rain than normal, and therefore the drainage system couldn't handle it,"
a Sderot shop owner told the Ynet news site.

"But what happened this time? There was a normal amount of rain, and
here we are, again with flooding, even worse than the last time."

The rain is expected to last until Tuesday in most of the country, with
sunny skies set to return on Wednesday, the Israel Meteorological
Society said.

The Sea of Galilee rose 1.5 centimeters (0.6 inches) from the rainfall,
an improvement for the body of water, which is at risk of being
depleted.

With the wind and precipitation, cold has also moved back into Israeli
cities. Jerusalem was predicted to experience lows of approximately 42°F
(6°C) and highs of 54°F (12°C) on Monday. Tel Aviv will feature
slightly higher temperatures, with lows of 52°F (11°C) and highs of 63°F
(17°C). Beersheba will see a high of 63°F (17°C) and a low of 48°F
(9°C), according to the IMS.

Similar temperatures are predicted for Tuesday, but they should increase
later in the week, when sunshine returns, according to IMS data.

Haifa and other northern coastal cities were predicted to have gusts of
wind of up to nearly 30 miles per hour, according to the IMS. Tel Aviv,
Jerusalem and Beersheba, meanwhile, can expect easterly gusts of nearly
25 miles per hour. - Times of Israel.

February 22, 2016 - GEORGIA, UNITED STATES - Booms so loud they have actually shaken homes were reported over the past two weeks in several Northeast Georgia counties.

Three reports were filed Sunday in the Maysville area of Jackson County,
but numerous other reports were made in Hall, Habersham and Madison
counties, authorities said Thursday. Several reports were filed the
previous week in the Commerce area of Jackson County.

"We've had a lot of people saying their houses are shaking and
describing it as sounding like a car crash to a tree falling," Banks
County Sheriff's Sgt. Carissa McFaddin said.

"The radius of where the reports are coming from is very wide, so it's not a concentrated area," she said.

"We really do not know what it may have been. I do know we've had a
number of military jets flying over that day," she said leading many to
believe the explosions are sonic bombs.

"Sonic booms would go over that distance," she said.

But McFaddin said others have suggested an earthquake, while Jackson
County Sheriff Janis Mangum said Thursday some suggested to her it was
someone exploding Tannerite, an explosive used to make exploding
targets. Tannerite is readily available to the public.

Nadin Humphries, a woman who lives outside Maysville, said Thursday "it sounded like a bomb went off. It shook my house."

"My son said he is familiar with those cannons they use to get rid of
vultures and they make a sound like that," she said. "We do have a rock
quarry down the highway that blasts from time to time, but was the first time I heard something that sounded like a bomb."

Reports of explosions of an undetermined source are not rare for the area.

"We've had these reports before and you don't find anything," Mangum said.

In Banks County the sheriff posted the booming mystery on the sheriff's
Facebook page and "it blew up very quickly. We had like 300 comments,"
McFadden said. - Athens Banner-Herald.

In the latest bulletin issued by PHIVOLCS at 6:00 pm, Bulusan Volcano's
ash fall occurred at 5:01 pm, which also reflected as an explosion type
earthquake that lasted for four minutes and twenty-one seconds.

PHIVOLCS detected a total of 12 volcanic earthquakes prior to the ash fall.

The agency raised Alert Level 1 over Bulusan Volcano and the public is
reminded not to go inside the 4-kilometer radius Permanent Danger Zone
(PDZ) due to risks of sudden steam and ash explosions.

WATCH: Phreatic explosions at Bulusan volcano.

PHIVOLCS said it is closely monitoring the volcano's activity and
advised residents located in the northwest and southwest sectors of the
volcano to take precautions against ash falls.

PHIVOLCS also reminded residents near valleys and river channels to be watchful against lahar.

Bulusan Volcano is the southernmost volcano on Luzon Island. It is
located in the province of Sorsogon in the Bicol region, 70 km southeast
of Mayon Volcano and approximately 250 km southeast of Manila.

It is considered as the Philippines' 4th most active volcano after Mayon, Taal, and Kanlaon. Its last eruption was in June 2015. - Manila Bulletin.

February 22, 2016 - HEALTH - Scientists claim they have managed to sequence the Zika genome,
while the head of the world's second-largest private funder of medical
research warns the virus is a larger threat than Ebola.

Saturday’s announcement in
Brazil is said to be more evidence of its link to cases of microcephaly
in affected countries - and a step toward developing a vaccine.

By understanding how Zika behaves in the human body and how it can be combated through tests and vaccines, Federal University of Rio de Janeiro (UFRJ) researcher Renato Santana said on TV Brasil, “What we know now may help us understand why the virus has chosen children's brain cells over those of adults - the pregnant women.”Jeremy Farrar, a former Professor of Tropical Medicine at Oxford University where the Zika virus "fighting" GM mosquitoes are produced, is now director of the Wellcome Trust, which announced this month it was sharing Zika virus data with the Bill and Melinda Gates Foundation and the National Institutes of Health.

He said that the “symptomless” Zika poses a greater threat than the Ebola outbreak of 2014 and 2015 which killed 11,000 people: “It is a silent infection in a group of highly vulnerable individuals – pregnant women – that is associated with a horrible outcome for their babies.”

The Zika virus has long been suspected of causing microcephaly in newborn babies, but until now, scientists were theorizing the connection.

Microcephaly is a rare condition where newborn babies have abnormally small heads and brains, causing impaired cognitive development.

About 4,000 infants in Brazil have been born with microcephaly since October, while in 2014 there were fewer than 150 cases.

“The real problem is that trying to develop a vaccine that would have to be tested on pregnant women is a practical and ethical nightmare,” said Mike Turner, former Professor of Parasitology at University of College and member of the Wellcome Trust.

The virus, which is transferred primarily through mosquitoes, has spread from Latin America to a number of US states, including Florida, Illinois, New Jersey and Texas. - RT.

Zika has been linked to birth defects. Now it may be causing paralysis

Liliana Zuñiga Ayarza sits at her home with
daughter Isabella Murillo remembering her mother, Belarmina Ayarza
Garcia, who was one of several recent deaths linked to Guillain-Barre
syndrome in Colombia. (Dania Maxwell for The Washington Post)

The Zika epidemic flaring across the Americas has produced several
hot spots with large numbers of cases. But there is no place quite like
Turbo.

The mosquito-borne virus has spread rapidly here and across lowland Colombia, but the city is unusual for the subsequent outbreak of a rare, debilitating disorder known as Guillain-Barre syndrome, whose precise link to the virus remains unclear. Before Zika’s arrival in Turbo, a mostly Afro-Colombian town of 60,000 set amid vast banana plantations on the country’s north coast, doctors typically saw one case of Guillain-Barre a year, if that.In the past six weeks, there have been five, all of them severe. Three patients have died. One is fighting for his life in an intensive care unit. The fifth, a 10-year-old girl, hasn’t been able to move her legs in a week.

The deaths, and the aggressiveness of the Guillain-Barre cases here, are among the first signs of a strange and worrisome pattern that is challenging the way doctors in Colombia and across Latin America are preparing for the spread of Zika.

Much of the global attention to the virus has zeroed in on a suspected link to microcephaly, a congenital defect that leaves babies with undersized heads and varying degrees of nerve damage. Brazilian officials say they may have hundreds or thousands of such cases related to Zika. But the photos of worried mothers and distressed infants may have given many people the impression that the virus poses no major risk to anyone else.That is not true, and certainly not here in Turbo, where rank sewage-filled canals line the streets and more and more people are arriving at the crowded emergency room with bloodshot eyes and itchy, red pockmarks, the telltale signs of Zika. Something about the virus – and researchers still don’t know what it is – appears to significantly increase the incidence of Guillain-Barre.The first resident here to get it was 41-year-old Eliana Uribe. She called in sick to her cousin’s dress shop one morning in mid-January, not long after missing several days of work with a strange rash and sore joints. Something was wrong with her feet, she said.

Katarina Lemus Uribe shows a photograph of her
cousin, Eliana Uribe Leon, shortly before she died from Guillain-Barre
after being infected with the Zika virus in Turbo. (Dania Maxwell for
The Washington Post)

Uribe’s family carried her to the emergency room. German Gomez, the internist at the small public hospital, thought it might be Guillain-Barre. But he wasn’t sure.

“I’d been here 15 months and hadn’t seen a single case,” he said.

Two days later, Uribe lost control of her tongue and facial muscles. She fell short of breath. Doctors rushed her to a bigger hospital.

Uribe died Feb. 2, her brain swamped in fluid – “severe hydrocephaly,” doctors told her family. “They never told us you could die from it,” said Katarina Lemus, Uribe’s cousin. What is hydrocephaly?

The day after Uribe’s death, another Turbo resident, Edelberto Padilla, 51, also died with Guillain-Barre, at a different hospital. He had the symptoms of Zika, too.

The Colombian government has confirmed three fatalities with Guillain-Barre, including two of the Turbo patients, blaming the deaths on Zika.

The U.S. Centers for Disease Control and Prevention (CDC) has confirmed two cases of Guillain-Barre related to Zika in the United States, presumably among the more than 80 travelers infected by the virus who have returned to the country. Another Guillain-Barre case was reported in Puerto Rico.

The normal prevalence rate for Guillain-Barre is one or two cases per 100,000 people, said Kenneth Gorson, a professor of neurology at Tufts University in Boston, who is one of the leading U.S. authorities on the disorder, named for the two French neurologists who discovered it exactly 100 years ago.

At its most basic level, Guillain-Barre is what happens when a patient’s immune system fights off an infection and then goes haywire, as antibodies turn against the body’s own nervous system, Gorson said. They attack nerve cells, apparently mistaking them for a virus. In some instances,the antibodies strip away the membrane that protects nerve endings, called myelin, leaving the body’s muscles essentially unable to communicate with the brain.In his courses, Gorson tells students that Guillain-Barre itself isn’t fatal. “What kills people is being paralyzed in an intensive care unit,” he said. “It’s the complications from being on a ventilator for long periods of time, the risk of blood clots, wound infections from lack of movement or other numerous medical complications that occur in paralyzed patients.

Access to quality care is critical.”Adults and children appear to be equally at risk of developing Guillain-Barre, but patients who already have health problems or compromised immune systems are less able to recover from it.One Guillain-Barre study in the Netherlands found a death rate of 1 in 20, “but that is with high-level care,” Gorson said. About one-quarter of patients need breathing assistance.Belarmina Ayarza, 58, contracted Zika while visiting her family in Turbo in January, then checked into a hospital in the city of Medellin 10 days later when she lost feeling in her legs. Doctors diagnosed Guillain-Barre, said her son, Jose Barrios. Ayarza was a diabetic, with high blood pressure. But her condition stabilized and Barrios was able to take her home in a wheelchair. On Feb. 7 she started convulsing in her bed. “I picked her up and held her in my arms,” Barrios said, “but she was gone.” Doctors said she’d had a heart attack.

Lack of high-level care

In the rural areas of Latin America where Zika is spreading, high-level care is often unavailable. Wait times at public hospitals, especially those swamped by Zika patients, can discourage patients from seeking care. Those with aggressive Guillain-Barre need complicated blood transfusions or a treatment known as immunoglobulin therapy to essentially wash out the harmful antibodies. But the treatments can cost more than $10,000, and patients may need several rounds.Colombia says that more than 30,000 citizens have been diagnosed with Zika so far, with 97 cases linked to Guillain-Barre. Brazil, Venezuela, El Salvador and Suriname have also reported a surge in the disorder. The same pattern appeared during the Zika outbreak in French Polynesia in 2013 and 2014, when at least 42 patients, most of whom were diagnosed with Zika, developed Guillain-Barre.

“We are seeing a spike everywhere that we are seeing the Zika virus,” said Tarun Dua, a neurologist at the World Health Organization (WHO). What’s unclear is whether Zika is causing Guillain-Barre or whether it is”cross-reacting” with antibodies from other widespread mosquito-borne viruses such as dengue or chikungunya.

Another major problem: There is no widely available, quick test for Zika, and the virus remains in an infected patient’s blood only for about a week. So it’s difficult to test for Zika in patients hospitalized with Guillain-Barre symptoms.

“The hypothesis is that Zika may be a more efficient trigger of Guillain-Barre, but we can’t say that at the moment,” said Anthony Costello, director of maternal, child and adolescent development at WHO. “The detective work is starting, but it takes time.”

In Turbo, patients diagnosed with Zika – whose symptoms include rash, joint pain, headaches and bloodshot eyes – are typically given acetaminophen and sent home to rest.

But they may share their homes with the Aedes aegypti mosquitoes that pick upthe disease from infected people and spread it. They breed in stagnant water.

Wilfrido Manuel Molinares looks out on a sewage
canal to arrive at his home in Turbo on Feb. 17. His daughter, Paula
Molinares, 10, is being treated for Guillain-Barre in Montería. (Dania
Maxwell for The Washington Post)

In a squalid neighborhood at the edge of a town known as El Bosque, the streets are unpaved and motorbikes weave around chickens and kids playing in the streets. Occasionally a truck rumbles through blaring advertisements on giant speakers, with an occasional public-health message urging residents to dump out standing water.

There are no health inspectors or fumigation crews to be seen. A foul, black bisque of sewage and trash oozes through a canal right in front of the home of Wilfrido Molinares. Children and horses walk through the muck; a frayed sofa sits half-submerged, rotting.

Molinares’s daughter Paula, 10, has been hospitalized with Guillain-Barre for nearly two weeks in the nearby city of Monteria. She had Zika symptoms before that. He’s had Zika, too, and was laid up from his construction job for two months last summer with chikungunya, which causes fevers and joint and muscle pain. Zika seemed mild compared with that, he said, until his daughter couldn’t stand on her own.

In their neighborhood, everyone stores drinking water in tanks, jugs and empty bottles.

“There are a lot of mosquitoes here,” Molinares said. “I bought mosquito repellent and spray it all over. But when the sun goes down, sometimes you can’t even sit outside.” - Washington Post.

Cuba sending 9,000 soldiers to fight Zika virus

Cuban President Raul
Castro says he is assigning 9,000 military personnel to efforts to keep
the Zika virus out of Cuba, calling on the entire country to help kill
the mosquito that carries the disease.

In a
front-page message on the state-run newspaper Granma Monday, Castro says
Cuba's fight to prevent the arrival of the virus has been hampered by
"the inadequate technical quality" of efforts against the mosquito,
insufficient work to clean up areas where the mosquito propagates and
poor weather conditions.

He says 9,000
military personnel and 200 national police officials will reinforce the
Public Health Ministry's efforts to spray neighborhoods for mosquitoes
and eliminate breeding spots. He says Cuba has yet to report a case of
Zika, which is suspected of causing birth defects in Brazil. - AP.

Brazil using drones to fight Zika

Brazil is trying out ever more inventive techniques to tackle
the Zika scourge –several cities will use drones to locate and destroy
breeding grounds for the mosquito, which has also been linked to dengue
fever and the chikungunya virus.

The drones have a very sharp eye. In San Paulo they perform low-altitude flyovers to detect signs of the pest in gardens, on terraces and other places where it is known to breed. They then fumigate the colonies, Xinhua reports.

Brazil has almost met its target of inspecting 60 million residences across the country. This adds to other efforts, such as massive armed forced deployment, to stamp out the infection. Some 40 percent of targeted locations have already been dealt with.

The idea of using the drones was born out of necessity. Many households were difficult to get into - some did not allow inspectors in, others simply had no one inside at the time. Drones greatly improve access without having to disturb residents.

Aside from drones and manpower, the government is also looking at newer and quicker means of diagnosing the virus, Sao Paulo Health Secretary Alexandra Padilha said.

WATCH: Brazil Navy informs school kids how to avoid Zika virus.

While revolutionary in Brazil, the idea of using drones to combat Zika isn’t new. A recent international show in the UAE – Drones for Good – dedicated to exploring the medical and life-saving potential of robotics and drones, showcased a very ambitious project.

Amicably called ROMEO (Remotely Operated Mosquito Emission Operation), the drone will fire off sterilized mosquitos over affected areas. Once the Zika-spreading female mosquitos mate with the sterilized male ones, the problem is solved. Female mosquitos mate only once in a lifetime, so the approach shows great promise.

About 4,000 infants in Brazil have been born with microcephaly since October, whereas in 2014 there were fewer than 150 cases.

The virus has spread from Latin America to a number of US states, including Florida, Illinois, New Jersey and Texas.

Zika was highlighted as a global health emergency in early February by the WHO. - RT.

February 22, 2016 - ATLANTIC OCEAN - On Feb. 6, 2016, around 14:00 UTC, a tiny chunk of interplanetary
material plunged into Earth's atmosphere and burned up — likely
exploding — about 30 kilometers above the Atlantic Ocean. The
energy released was equivalent to the detonation of 13,000 tons of TNT,
making this the largest such event since the (much larger) Chelyabinsk
blast in February 2013.

OK, so first, off: Don't panic! As impacts go, this was pretty small*.
After all, you didn't even hear about until weeks after it occurred.
Events this size aren't too big a concern. Had it happened over a
populated area it would've rattled some windows and probably terrified a
lot of people, but I don't think it would've done any real damage.

For comparison, the Chelyabinsk explosion, which was strong enough to
shatter windows and injure over 1000 people (due to flying glass), had
an equivalent yield of 500,000 tons of TNT, 40 times the energy of this
more recent impact.

I talked about events like this for Crash Course Astronomy:
A little background: The Earth is bombarded by debris from space to the
tune of about 100 tons every day. Most of this stuff is quite small,
like the size of a grain of sand or smaller, and burns up 100 kilometers
or so off the ground. We call the solid bit of debris a meteoroid, the
bright phenomenon a meteor, and, if it hits the ground, a meteorite.

If the piece is bigger, it can get deeper into our atmosphere before
burning up. Moving at orbital speeds, they can enter our atmosphere from
roughly 10 - 100 kilometers per second. For comparison, a typical
rifle bullet moves at one kps. As they plow into the air, they compress
the gas in front of them violently, heating it up. This in turns heats
up the meteoroid, which starts to glow. Material can vaporize and blow
off (this is called "ablation"), and usually within seconds the
meteoroid is either slowed so much it no longer glows, or it vaporizes
entirely.

If it's much bigger, centimeters or more across, it can start to
disintegrate as the air in front of it imparts enormous pressure on it.
It flattens (called "pancaking"), and breaks up. Now we have several
smaller pieces, and each starts to burn up; the increase in surface area
means more heating and glowing, then those pieces break up and get
smaller, and you get a runaway cascade. This happens very rapidly on a
human timescale; the Chelyabinsk asteroid broke up is it came in and
this was seen as a series of very bright pulses of light. It can happen
so rapidly that it may as well be called an explosion; a huge amount of
energy released all at once. In the end, the huge energy of motion (the
"kinetic energy") is converted into light and heat (and also to break up
the meteoroid).

Given the explosive energy of the Feb. 6 meteoroid, if it were
made of rock like the Chelyabinsk asteroid then it was very roughly 5-7
meters across; the size of a large living room, say. I
calculated that by a straight comparison to Chelyabinsk: We know that
was from a rock about 19 meters across; the energy released scales as
the mass, and the mass increases with radius cubed for a sphere. So this
is all approximate with a few guesses thrown in, but it's probably
close.

It would've been a dramatic sight to say the least. But, it
happened about 1000 km off the coast of Brazil, ESE of Rio de Janeiro.
That's far enough out over the ocean that it's unlikely anyone saw it. So how do we know about it?

Good question. The report came to the JPL folks via the US government; as you might imagine, various arms of the military are curious indeed about atmospheric explosions.However, not much information is revealed by the source;
just the time, direction, explosive yield, and things like that. I can
think of three ways to detect a big fireball in this case: Satellite
observations, which would image them directly; seismic monitors, which
can detect the explosion as the sound wave from the blast moves through
the ground; and atmospheric microphones, which can detect the
long-wavelength infrasound from an event. This may have been detected by
any combination of these (though since it was over the open ocean,
seismic monitors seen unlikely).

Impacts like this happen several times per year on average, with most going unseen. The Earth is mostly water, and even where there's land it's sparsely populated overall.Chelyabinsk
was both relatively energetic and happened over a populated area (the
city of Chelyabinsk has over a million people). Still, I would assume the military sees most if not all events this size,but chooses not to report them for their own reasons.
I understand the desire for them to keep their technology and
capabilities secret. It would be nice scientifically to have this data
available, but then again they don't have to release any of it at all,
so even having this much is better than nothing. And it's useful.

And as usual, all of this underscores the need to be on the lookout. A
rock this small is almost impossible to see more than a few hours before
impact, but the flip side is that it's also really unlikely to do any
damage. But once they get into the 20 - 50 meter range that changes; explosions from impacts like that rival nuclear bombs.
Happily, they're very rare — here we're talking fewer than once per
century, statistically speaking — but it would be nice if we knew they
were coming. It's hard to say just what we would do if we saw one, but right now we don't even have that option.

February 22, 2016 - ICELAND - The Great Geysir, Iceland's most famous hot spring, which has given the
name to geysers all over the world, erupted yesterday. This rare event
was captured on camera.

Halldóra Eldon, who works at Hótel Geysir was at work when she noticed
an unusual amount of steam rising from Geysir. "It was just by chance
that I was looking out of the window. I decided to walk outside and it
started erupting."

She says it's a very unusual sight although staff of the hotel saw the
geyser erupt twice last summer. "I've worked here for two years and I
never saw this happening before."

Earthquakes have been shown to revive the activity of Geysir and records
from 1630 show that it erupted violently many times that year. Until
1896 however the hot spring was almost dormant before an earthquake that
year caused eruptions to begin again, several times a day.

In 1935 a man-made channel was dug through the rim which caused a
revival in activity, but gradually the channel became clogged with
silica making eruptions once again rare. In 1981 the channel was cleared
and eruptions were simulated on special occasions by the additon of
soaps, something later discouraged because of environmental concerns.

An earthquake in the year 2000 revived the geyser again and an eruption
took place for two days straight, reaching 122 metres in height. In the
last decade, eruptions have decreased considerably and it is now
considered almost inactive.

"All the dogs in the neighbourhood are going nuts," D.D.O.
resident Adria Morrell posted to Facebook around 10 p.m. She recorded
the noise, which sounded like wind through wires or wind chimes.

There was no wind at the time, she said, and soon after she posted,
other West Island residents recounted their own spooky aural encounters.The sound was reported to have lasted more than an hour.

WATCH: Strange noise over Quebec.

This sort of event isn't unheard of.Similar things have happened in Montana, Australia, Germany and British Columbia. Though there's no clear explanation,reports say NASA has theorized that it could be the "background noise of the earth."

"These natural radio emissions from the planet are very much real," Tech Times reported NASA as saying. - National Post.

February 22, 2016 - CHILE - A magnitude 6.0 earthquake has struck off the western part of the Chilean coast, according to the national seismological center.

The US Geological Survey has measured the quake at magnitude 5.9, with the epicenter located some 84km west of Ovalle, Chile.

The quake was very shallow and struck some 10.2 km (6.3 miles) below the seabed.

There were no immediate reports of damage or casualties from the tremor.

Strong shaking was felt in the area of Atacama Desert in the north of the country, according to local authorities, who are in the process of assessing any possible damage.

USGS shakemap intensity.

In the meantime, the Chilean navy said they were not expecting a tsunami and were not issuing an alert. In September last year, a massive 8.3 earthquake triggered tsunami waves which reached Chilean shores, flooding the streets and forcing people to seek shelter on higher grounds.

At the time, the Chilean coastal city of Coquimbo was been hit by waves measuring up to 4.5 meters above normal sea level. At least five people were killed and one million people were evacuated from the affected areas.

The September quake and tsunami were the largest to strike the country since April 1 2014, when a magnitude-8.2 earthquake impacted just off the Chilean coast, near Iquique. A quake in February 2010 registered magnitude 8.8. The most powerful quake overall occurred near Lumaco, Chile, in May 1960 registering 9.5. All of them generated tsunamis in the country, located on the so-called Pacific ring of fire, renowned for being prone to earthquakes.

Seismotectonics of South America (Nazca Plate Region)

The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.

Most
of the large earthquakes in South America are constrained to shallow
depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.

USGS plate tectonics for the region.

Large intermediate-depth earthquakes
(those occurring between depths of approximately 70 and 300 km) are
relatively limited in size and spatial extent in South America, and
occur within the Nazca plate as a result of internal deformation within
the subducting plate. These earthquakes generally cluster beneath
northern Chile and southwestern Bolivia, and to a lesser extent beneath
northern Peru and southern Ecuador, with depths between 110 and 130 km.
Most of these earthquakes occur adjacent to the bend in the coastline
between Peru and Chile. The most recent large intermediate-depth
earthquake in this region was the 2005 M7.8 Tarapaca, Chile earthquake.

Earthquakes
can also be generated to depths greater than 600 km as a result of
continued internal deformation of the subducting Nazca plate. Deep-focus
earthquakes in South America are not observed from a depth range of
approximately 300 to 500 km. Instead, deep earthquakes in this region
occur at depths of 500 to 650 km and are concentrated into two zones:
one that runs beneath the Peru-Brazil border and another that extends
from central Bolivia to central Argentina. These earthquakes generally
do not exhibit large magnitudes. An exception to this was the 1994
Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, which was until recently the largest
deep-focus earthquake instrumentally recorded (superseded in May 2013 by
a M8.3 earthquake 610 km beneath the Sea of Okhotsk, Russia), and was
felt widely throughout South and North America.

Subduction
of the Nazca plate is geometrically complex and impacts the geology and
seismicity of the western edge of South America. The intermediate-depth
regions of the subducting Nazca plate can be segmented into five
sections based on their angle of subduction beneath the South America
plate. Three segments are characterized by steeply dipping subduction;
the other two by near-horizontal subduction. The Nazca plate beneath
northern Ecuador, southern Peru to northern Chile, and southern Chile
descend into the mantle at angles of 25° to 30°. In contrast, the slab
beneath southern Ecuador to central Peru, and under central Chile, is
subducting at a shallow angle of approximately 10° or less. In these
regions of “flat-slab” subduction, the Nazca plate moves horizontally
for several hundred kilometers before continuing its descent into the
mantle, and is shadowed by an extended zone of crustal seismicity in the
overlying South America plate. Although the South America plate
exhibits a chain of active volcanism resulting from the subduction and
partial melting of the Nazca oceanic lithosphere along most of the arc,
these regions of inferred shallow subduction correlate with an absence
of volcanic activity.